1. Field of the Invention
In general, the present invention relates to synthetic building materials that can be used in place of traditional lumber and wood products. More specifically, the present invention relates to the manufacture and use of cement-based, pre-stressed or post-tensioned compositions that are formed into synthetic lumber.
2. Prior Art Description
Wood has been used as a building material throughout human history. Wood is a nearly perfect building material. It is lightweight, strong, and flexible. Wood can be cut, carved, and sanded into almost any shape using only simple handheld tools. Furthermore, in the past, wood has been both plentiful and inexpensive. However, as forests retreat, wood is becoming increasingly more expensive. Additionally, the quality of wood has been decreasing as younger trees have been forested to meet the world's demand for wood products.
Although wood is a highly versatile building material, it does have some disadvantages. Wood, being an organic material, is vulnerable to rot, insect damage and degradation from both the elements and a host of microorganisms. Accordingly, wood must be treated and/or painted, especially if it is left exposed to the elements. Additionally, although wood has an average strength, no two pieces of wood have the same properties. The strength, flexibility, density and even appearance of a piece of wood depends largely upon the type of tree from which the wood came, the part of the tree from where it was cut, the direction of grain in the wood, and the number of knots and other imperfections that are present in the wood.
In an attempt to make building materials that are more uniform and more resistant to the elements, synthetic compositions have been used in place of wood. Many traditional wooden products, such as deck components, are now made from synthetic materials. The synthetic compositions used to make traditional wood building products vary. If the building product is ornamental, it may be molded from plastic. However, if the building product must withstand static or dynamic loading, the building product is typically made by mixing either filler or wood with a cement or a plastic binder. Synthetic building products made from such compositions are typically much more resistant to rot and insects than natural wood. Furthermore, such synthetic building products are also far more uniform in strength, flexibility, density, and appearance from piece to piece. However, such synthetic building products are typically heavier, subject to creep, more brittle, and much weaker than natural wood products. Such synthetic building materials also tend to be considerably more expensive than those made from natural wood. Accordingly, many synthetic building products have not found wide acceptance in the marketplace.
The products and uses for such building materials comprise many applications. One of the larger market applications for synthetic building materials is the market for outdoor decks and boardwalks. The construction techniques used to build decks and boardwalks are complex and involve the use of many columns, piers, beams, joists, and deck planks. Consequently, considerable materials, fasteners, and labor are required to construct decks and boardwalks.
A need therefore exists for a new composition for synthetic structural building materials that more closely mirrors the strength, flexibility, span distance, and tensile strength of wood, while still providing better resistance to weathering and insects. A need also exists for a composition and shape for such synthetic structural building materials that can be manufactured inexpensively so as to compete with the costs to design and build with the natural wood products. A need further exists for a construction system that simplifies the construction of deck and boardwalk projects. These needs are met by the present invention as described and claimed below.